Stoker control



E. K. SCOGGIN STOKER CONTROL July 15, 1947.

2 sheets-snee@ 1` Original Filed Feb. 24, 1936I Ihr/02122.07

@meg ,4M

@WKN

July 15, 1947. E Kscogsm Re.22,s98

` STOKER CONTROL Original Filed Feb. 24, 1936 2 Sheets-Sheet 2 bmnfnseg,in .59,72715-.z7fornyey V/fl/"Sf "l M -Reisss'ue'd July 15, 1947 STOKERCONTROL Elmer K. Scoggin, Golden Valley, Minn., assignor to MinneapolisRegulator Company, Minneapolis, Minn., a corporation of DelawareOriginal No. 2,234,383, dated March 11, 1941,

Serial No. 65,226, February 24, 1936. Application for reissue December1, 1941, Serial No.

33 Claims. 1

This invention relates to controls, and more particularly to a type ofcontrol adapted to regulate feeding of fuel to a re under predeterminedtemperature conditions and/or at predetermined time intervals.

One object of this invention is the provision of an improved controlsystem arranged to operate a mechanism, such as an automatic Stoker,upon a predetermined fall in temperature to control the said temperaturein a space to be heated, or at predetermined time intervals in theabsence of such a temperature drop, in order to maintain combustion ofthe fire at all times.

Another object is the provision of a system which will automaticallypreclude the operation of a stoker under the control of a timed mechansmduring, and for an appreciable interval after, operation of the stokerby a temperature responsive mechanism, such as a conventionalthermostat.

A further object is the provision of a system wherein continuedoperation of a stoker by temperature controlled means after energizationby timed mechanism is precluded in the absence of a call for heat in thespace to be heated.

Still another object is the provision of improved mechanism forcontrolling intermittent timed feeding of fuel to a source ofcombustion.

A further object is the provision of suitable mechanism to vary theduration of a period during which fuel is fed to a re under the controlof timed mechanism.

A still further object is the provision of means to vary the intervalbetween the timed operations of a timed fuel feeding controlmechanisrn.

A more specific object is the provision of improved mechanism toaccomplish the above and other objects, which will be durable inconstruction and reliable in operation.

A further specific object is the provision in a system including athermostat and a timer mech` anism, of an auxiliary temperatureresponsive circuit controlling mechanism in the thermostat circuit.

Other objects will in part be obvious and in part be pointed outhereinafter.

Accordingly, the invention consists in the arrangements of parts,combinations of elements and features of construction, as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings, wherein is shown one of the variouspossible embodiments of this invention:

Figure 1 is a schematic view showing certain parts of the structure ofthe instant invention and a diagrammatic representation of one form ofcontrol circuit;

Figure 2 is an enlarged sectional elevation taken substantially alongline 2-2 of Figure 1;

Figures 3, 4 and 5 are detailed views of certain portions of thestructure shown in Figure l, showing certain movable parts in dilferentpositions;

Figure 6 is a detailed view showing another portion of the structure ina different position, and

Figure 'l is a sectional view taken along line 'I-T of Figure 6. y

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Referring now to the drawings and more particularly to Figure l: asuitable motor, generally indicated at II), which may serve to drive anysuitable apparatus such, for example, as an automatic stoker (notshown), to feed fuel to a furnace, is controlled, in a manner to behereinafter described, by the conjoint action of a suitable thermostat,schematically indicated at I I, and a timer mechanism, generallyindicated at I2. Timer mechanism I2 is so constructed and arranged as tooperate motor I0 for a predetermined period at suitable intervals, suchas, illustratively, four minutes every half hour, such periods andintervals being subject to variation at the will of the operator.Provision is also made to render timer mechanism I2 ineffective whenmotor I0 is in operation under the control of thermostat Il during thenormal operating period of timer mechanism I2 and for a suitable periodsubsequent to the cessation of such operation. One system andarrangement of parts adapted to accomplish the above and other resultswill now be described.

Timer mechanism I2 includes a suitable motor I3 which may be of thesynchronous type, having a iield winding I4 to which current is suppliedthrough lead wires I5 and I6 from suitable line wires Il and I8, whichin turn lead to a suitable source of electrical energy (not shown). Apair of cams i9 and 20 are coaxially mounted, in a manner to behereinafter described, on a sleeve 22 and rotated in a counter-clockwisedirection as indicated by the arrow in Figure l, through suitablegearing and friction mechanism, also to be described hereinafter, bymotor I3. Cam I9 is preferably constructed in such a manner as tovhavetwo oppositely disposed low surfaces I9a with intervening high surfaces|91). A suitable faces 25a of a peripheral extent slightly less than theperipheral extent of low surfaces I9a. Suitable indicia 2Ilb may besuitably affixed. toer imprinted on a portion of thesurface. of ,cam

29. A stud 2| having a threaded end isprovided,v

for engagement with a suitable aperture in cam 2U.

By reference to Figures l and 2 of the drawings,V it will be seen thatwhen the parts. are irl/assembled relation stud 2| is passed throughslot 19j and threadedly engaged with cam 20, and indicia 2919 ispositioned below and adjacent aperture |911 in alignment with pointer|9e. By loosening stud 2| cam 2G, maybe rotated about sleeve 22 withrespect tocam I9 and thecomposite high surface area of cams I9. andZIJ,which includes the total of the high surface areas |91) and 29a,1nay bevaried. Indicia 29h will be correspondingly varied with respecttopointer I9e and accordingly may indifcate,.in theform of timeindications, as will be explained hereinafter, thecombined low surfacearea of cams I9 and 2D.

Having particular reference to Figure 2, it will be seen that motor |3has a drive shaft 23 to which is aixed a suitable pinion 24 whichengages a reduction gear 25. Pinion 24 is driven through a suitableconventional reduction train (not shown). Gear 25 has an axle 26journaled for. rotation in a sleeveZBa. secured toa mounting bracket 21.Mounting bracket 21 may be secured in any suitable manner, as by screws28, vto an insulating panel.29 which may comprise a portion of asuitable casing (not shown).- Axle 26 carries atone end a secondreduction .gear 3|) which engagesa driven gear3| which is mountedonsleeve 22. Gear. 3| may have a diameter substantially equaltothat ofgear 25 in order that sleeve 22` and shaft .23`1nay be in substantialalignment. VA suitablefriction disc 32, which may be of any desiredmaterial but for which, in practice, cork has been found advantageous,is mounted onsleeve 22 adjacent gear 3l. Cams 20 and I9 vrespectivelyare then superimposed on disc 32. A stud vmember 33, suitably mounted inpanel 29, passes through the interior of sleeve 22 and serves asV anaxle for rotation .of sleeve 22 thereabout. Sleeve 22 has a flangedannulus 22a for abutment witharim 33a .of vstud 33... A housing 34 holdsa spring 35; positioned about the exterior periphery offsleepve .22, inclose juxtaposition with the exterior face of .cam I9. A washer 36 maybe superimposed overtheyouter end of housing 34 and held in place by thecoaction of a spring -collar 31 ,with a suitable groove 331) adjacentthe outer end of axle 33-` It .will now beseen that rotation of shaft 23is imparted to cams yI9 and 20 through sleeve 22. and the chain vo-f-reduction gears 24, 25, 30 and 3|.. In` practicefit has been founddesirableto arrange.thegearing-ratio in such manner that cams I9 and 20make one complete rotation every. hour.

It lwill further be seen that friction dise 32 providesr means wherebycams I9 and 20 may be rotated with respect to sleeve 22 .for any desiredpurposeJ vsuch as adjustment of the timer mechanism above described.

A cam` follower assembly, generally indicated aty gage a suitablethreaded opening-in cam TIS to f 49, is pivotally mounted adjacent aportion of the exterior periphery of cams I9 and 20. Cam follower 49 iscomprised of a block 43 of suitable insulating material on which aremounted by any suitable means,. such as screws 44,.a plurality,illustratively three, of spring contact arms 45, 46 and 41, the purposeof which will be described hereinafter.

It will now be seen that the cam assembly comprised-of cams I9 and 20rotates adjacent cam follower. 4D and presents thereto at spacedintervals alowsurfacefla of cam I9. The area of surface |9a-isdetermined by the relative position of an adjacent highsurface 20a ofcam 29. Variation of the l position'of high surface 20a with respect to'lowsurface I9a correspondingly varies the position of indicia 29hwithrespect to pointer I9e. Since the cam assembly rotates once an hour eachlow surface Illa, except under circumstances to be hereinafterdescribed, is juxtaposed to earn follower 4D fora period of minutesduring each hour.` Indicia 201),v therefore, may be calibrated todesignate minutes and the position of pointer I9@ with respect theretoaccordingly indicates the number of minutes during each hour prise amounting member 4|'to which block 43 may besecured by-any suitablemeans, such as screws 42. Mounting member 4| may be pivotally mounted onpanel 29 through pivot 49y and secured, as by a spring collar 5B. Aspring 5| se"- cured to an arm 4|a extending from mounting member 4|,and a nxed point on panel 29, such as screw 28, -(see-Figure-2), is sodesigned and positioned as normally to hold block 43 adjacent theperipheryof cams |9and 29. A downwardly depending lug48having a cam.surface 49a and a latching surface 48h, for a purpose to be hereinafterdescribed, is also aflixed to mounting member 4I and may comprise anintegral part thereof.

It will now be seen that the timed rotation of cams I9 andi!!! causescamfollower 4|! to drop a distance equal to the difference between highsurface |91) and-low surface I9a, due to the combined .forcev of gravityand spring 5I each time' a lowsurfacearea of the cam assembly rotatesinto engagement with block 43, and that cam follower 4D is held inraraised position for the period during .which the high surface `|9bof camI9 is adjacent thereto. The fall of cam follower 49 to its low positioncauses the closure of -a circuit in a manner and for-a purpose tobehereinafter described, while -a subsequent rise of cam follower 4(1.byljuxtaposition to high surface |919 of cam I9 causes .the circuittore-open.

While in the preceding vdiscussion cam'l9 has been pointed out ashavingv a pair of oppositely .disposedlow surfaces in order to permit adrop a drop .may occur only once during every fulll rotation of cam I9.The mechanism for accomplishing.thiscomprises a segment 55, one sur#face 55a of which is comprised of an arc having a radiusof curvature-Ysubstantially equal to high surfaceV |913` yof caml I9,1and the'othersurface 551)u of which. is comprised of an arc having a radius ofcurvature. equal'to-low surface ISaof cam I9. A projection 55o formed onsurface 55h is substantially equal incontourand'dimensions to projection|9c on cam I9. `A securing screw 56 'passing` throughan aperturel insegment 55 may enhold segmentl 55 in related assembly with cam I9.Additional securing means t prevent rotation of segment 55 about screw55 may be provided in the form of an aperture 55d in member 55 and asuitable projection |99 on the surface of cam I3 adapted to engagetherewith (see Figure '7 From the above it will be seen that the portionof the peripheral configuration of the cam assembly adjacent segment 55may be varied by a simple reversal of segment 55 to the position shownin Figure 6 by release of screw 56. It will also be seen that whensegment 55 is in the position shown in Figures 1, 3, 4 and 5 of thedrawings both low surfaces Isa of cam |3 will be juxtaposed to camfollower 40, but that when the position of segment 55 is reversed, as inFigure 6, that portion of the cam assembly adjacent segment 55 willpresent an unbroken high surface area. Accordingly, when segment 55 isin the position shown in Figures 1, 3, 4 and 5 of the drawings camfollower 40 will drop twice during each full, or illustratively, hourly,rotation of the cam assembly comprising cams I3 and 20 and segment 55,to close a circuit and actuate stoker motor |0, as will be hereinafterset forth. But when segment 55 is reversed in the position shown inFigure 6, such actuation will occur only once during each hour.

As shown in Figures 1, 3, 4 and 5, in dotted lines a lever 60 ispivotally mounted as by means of a pivot 6| on, and to the rear of,operating panel 23. A projection 63a extends forwardly from lever 60through a suitable aperture 29a in panel 29 immediately adjacent lug 43,and a second projec tion 60h extends from lever 60 through an aperture23h at a second point spaced from aperture 29a. Projections 60a and 60hare adapted to be moved in a manner and for a purpose set forthhereinafter, and apertures 23a and 29h serve not only to permit passageof projections 60a and 00h through panel 29, but also as stops to limitthe movement thereof. A suitable extension, which comprises a weight60o, extends beyond pivot point of lever 60' and serves normally to holdlever 60 at the extreme limit of pivotal rotation in a clockwisedirection, such limit, as above stated, being defined by engagement ofprojection 29a and 23h with the right hand (as seen in the drawings)walls of their associated apertures 60a, and 6012 respectively. Apivoted spring arm 62 is mounted adjacent projection 60b and is adaptedto be actuated in a manner to be hereinafter described toward and awayfrom projection 60h.

The fall of insulating block 43 upon engagement with low surface ISa ofthe cam assembly, as above stated, closes a circuit in a mannerhereinafter described, which serves to draw arm 62 to the left as viewedin the drawings. Likewise, the closing of a circuit by thermostat I in amanner to be described hereinafter also draws spring arm 62 to the leftas shown in Figure 1.

Referring now particularly to Figure 3, insulating block 43 is shown inengagement with the low surface |0a of cam |9. The circuit is now closedby means of cam follower 40 and spring arm |52 is shown as bearing tothe left against projection 60h of lever 60. The pressure of spring arm62 overcomes the gravitational pull of weight 60o and causes projection60a, to abut the inner surface of lug 48. Upon continued rotation of thecam assembly engagement of high surface |35 with insulating block 43will cause cam follower 40 to rise and break the circuit, which will inturn release the pressure of arm 60 against projection 60h and permitthe parts, with the exception of `a wire 99 leads to arm |03.

the continuously rotating cam assembly, to return to the position asshown in Figure 1.

Should spring arm 62, however, be actuated by thermostat whileinsulating block 43 is in engagemenl-l with a high surface portion |9bof cam |9, spring arm 52 will engage projection 60h and force projection00a into engagement with cam surface 48a and therealong into engagement,with latching surface 48h. Upon release of the pressure of arm 62 theparts will remain in the position as indicated in Figure 4, withprojection 60a engaging latching surface 48h even after low surface |9ahas rotated to a position adjacent insulating block 43, until continuedrotation brings the parts into the position shown in Figure 5, whereuponprojection |30 raises insulating block 43 and hence cam follower 40 to aheight sufficient to release projection 50a from engagement withlatching surface 48h of lug 48. Thereupon weight 60e turns lever 60about its pivot El until projection 60a again abuts the righthand wallof aperture 23a.

It is to be noted that projection is adjacent an end of low surface I3ain a direction counter to the direction of rotation of the cam assembly.Accordingly, it will be seen that if cam follower 43 and lug 48 are insuch position as shown in Figure 4 as to necessitate release fromengagement with projection 60a by action of projection |9c, it will beimpossible to close the circuit associated with cam follower 40 for adefinite period, subsequent to the release of projection 60a fromengagement with latch member 48h, This period is of a durationsufficient to permit an entire high surface |9b to pass.,cam follower 40before the presentation of a low surface |3a to permit cam follower 40to drop.

It may here be pointed out that with the parts, including segment 55, inthe position as shown in Figures 1, 3, 4 and 5 of the drawings,projection 55o serves the same purpose and acts in the same manner asprojection |90.

Having particular reference to the wiring diagram shown in connectionwith Figure l, line wires I1 and I0 lead through the primary |00a of asuitable step-down transformer |00. A wire |0| leads from one side ofthe secondary |0017 of transformer |00 to a coil |02a of a relay,generally indicated at |02. Relay |02 includes contact arms |03, |04,|05 and is also operably associated with spring arm 62. In practicalform spring arm 62 may comprise an extension of one of the arms |03, |04or |05 of relay |02. A wire 91 leads from the side of relay coil |02aopposite wire |0| to a junction 38 from which A wire 96 leads fromjunction 98 to a junction |06 from which extends a wire |01 to a contact|08 which is adapted to engage opposite contact |08 carried by springarm 41 of cam follower 40'. A second wire |09 also leads from junction|06 to a contact |I0 adapted to engage an associated contact ||0 carriedby bimetallic thermostat A wire leads from terminal ||2 of thermostat toa contact ||3 which is adapted to engage an opposed contact ||3 carriedby spring arm 45 of cam follower 40. The arm 46 of cam follower 40 bearsa contact ||4 at an end thereof, adapted to engage a contact H4. A Wire||5 leads from contact ||4 to a junction H6, from which a wire leads totransformer secondary |00b at the side opposite wire |0|. A second wireI8 leads from junction ||6 to a mercury switch ||3 associated with athermostatic element |20 for a purpose to be more fully describedhereinafter, and a second wire |2| leads from mercury switch IIS to acontact |22 positioned adjacent a corresponding rcontact |22' carried.vby a, VInovable arm of thermostat II.

Arm |03 of relay |02 is adapted under circumstances to be hereinafterdescribed, to engage a contact |23. A wire'l24 leads from contact |23 toa terminal |25 carried by cam follower 40. Terminal |25 may, inpractice, comprise one of holding screwsl 44, provided'electricalcontact is established therethrough with arms 45, 40 and 41 and hencecontacts' II3', II4 and |08. Arms |04 and I '0`5 are adapted to engagerespectively contacts" |26 and |21which in turn are'connected with Wires|28 and I 29 respectively, leading from line wires I1 and I8. Theopposite ends of arms |04 and |05 are connected through wires |30 andI'3l respectively to motor I0. Accordingly, it will be seen thatenergization of relay I 02 in a manner to `be` explained hereinafter,will cause arms I`4 and'l05 to engage contacts |26 and |21respectivelyand operate motor I0 directly from line wires I1 and I8.

Assuming now that the parts are in the posi- ,tion shown in Figure l, itwill be seen lthat no circuit Ais closed through relay coil |02a and inconsequence arms |03, |04 and |05 are open andl spring arm I52 exerts nopressure on projection 50h.

Now, Yhaving particular reference to the circuit `controlled by timermechanism I2, Vassume that the cam assembly comprised of cams I9 and 20has rotated to the position shown in Figure 3. Insulating block 43 willdrop, permitting contactsIIII and I08to engage respectivelycontacts |I4and |00. An energizing circuit is'gnow established from transformersecondary ',I00b through `wire IDI, relay coil |02a, wire 91, junotion98, wires 9E and |01, contacts IBB-|08', arms 41 and 45, contactsII4-II4, wire H5, junction IIB, and wire I I1 back to transformersecondary |001), which serves to energize relay |02. Arm |03 is nowpulled inwardly to engage contact I 23, whereupon a holding circuit isestablished from transformer secondary |0012 through wire |0I, relaycoil |02a, Wire,91, junction 93 as above described, and thence throughwire 99, arm |03, contact |23, wire |24, terminal |25, arm 40, contactII4 to vcontact II4- II4,l wire II5, junction IIB and wire II1 totransformer secondary |001), wires 95 and |01 and contact |08, |08 beingshunted out. Simultaneously, with the closing of arm |03, arms |04 andY|05 engage contacts |26 and |21 and stoker motor I0 is placed inoperation. Likewise, simultaneously spring arm 6 2Ybears againstprojection 50h and forces projection 60a into engagement with theright-hand surface of lug 48, as shown in Figure 3. Upon `furtherrotation of the cam assembly a high surface I9b raises insulating block43 and breaks, rrst, contacts |08-I08 and in a relatively short timethereafter contacts |I4-II4'. It will be'seen from the description ofthe ycircuit'abwe given that motor I0 continues to operate untilcontacts I4--||4' are broken and in the absence of any activity on thepart of thermostat |I, still assuming it to be inthe open position shownin Figure l, the circuit through'relay coil I02a is broken to permitarms |03, |04 and |05 to move away from their respective contactsandjlik'ewise to permit spring arm 02 to'release Vits pressure onprojection 60h. Inthe 'continued 'absence of activity o-n the part ofthermostat |I 'this cycle will be continued at hourlyv orhalfhourlyintervals, ,depending upon the position of segment55, and such actuationof motor I0 will be vfor a "period to be determined by the relationshipof cams I9 and 20 with respect to each other.

Assume now, with reference to the circuit controlled by thermostat I I,the parts, including the timer mechanism I2, being in the position shownin Figure l, that there is a call for heat in `the space, thetemperature of which is adapted to be controlled by thermostat |I.Contacts I22--I22 close and after an interval and upon a further drop intemperature contacts IIO-IIO close. The purpose of this plurality ofcontacts will be described hereinafter. A circuit is now established'through contact |22, wire I2I, mercury switch yI I9, assuming switch IISis closed, which it willbe except under certain conditions to behereinafter setforth, wire IIB, wire II1, transformer secondary |00b,wire IDI, relaycoil I02c, wires 91,796 and |09, contacts IIO-I I0',thermostat I I `and contact |22. This circuit serves also to energizerelay coil I02a and close its associated contacts to establish a holdingcircuit from transformer v|00 through wire IDI, relay coil |02a, wire91, junction 98, lwire S9, arm |03, contact |23, wire |24, terminal |25,arm 45, contacts ||3I I3', wire ||I, terminal IIZ, thermostat II,contacts I22-I22", wire I12I, mercury switch I I 0, wire IIS, junctionII6, wire I|1 back to transformer secondary |005. Contacts I|0'-IIO andwires |09, |06 and 90 are shunted out. Spring army E2 is likewiseactuated causing projection a to be pulled into latching engagement withlatching surface 48h of lug 48. 'Simultaneously stoker'motor I0 is putin operation. It will now be seen that upon, continued rotation of camI9 to the position as shown in Figure 4, wherein it presents a lowsurface I9a to cam follower 40, projection 60a serves to hold camfollower 40 through latching surface 48h in the same position as thoughit engaged a high surface, yand accordingly will not permit closing ofthe circuit through contacts I |4-| I4', and IUS-|09' as previouslydiscussed.

If, however, during the time low surface area ISa is adjacent camfollower 40 and the requirement for heat in the space to be heated hasbeen satisfied, relay |02 is deenergized andpressure on the spring arm-62 ycorrespondingly released, whereupon the engagement of projectionISC or projection 55C, as the case may be, with insulating block 43 willserve to lift lug 48 out of latching engagement with projection 60a andpermit the'same to return to'the position shown in Figures'l and 5 underthe impetus'of weight 00o. The system is now in condition for operationby the tmer'mechanism upon the next'presentation of a'low surface I 9ato cam 'follower 40.

If, however, during the period immediately followingrelease by one ofthe projections I9c or 55o, thermostat II again responds to a call forheat and closes the circuit through relay |02,

projection 60a will again engage latching member 48hy and the cycle willbe repeated.

Accordingly, it will be seen that under such circumstances as abnormallycold weather when the room'thermostat makes frequent and/or prolongedcalls'for heat, the'timer mechanism may rotate for an indefinite periodwithout 'actuating the stoker, but that under other conditions, suchk asan unusually warm spell of weather, the timer mechanism will serve tomaintain a fire in the' furnace even though no demand for heatwhatsoever is made `bythermostat I I. It will further be seen that thetimer mechanism is rendered incapable of operating the stoker duringactuation by the thermostat II and for a period subsequent thereto. Sucha period may vary from, at a minimum, approximately a half an hour,assuming that thermostat I| satisfies the call for heat in the space tobe heated immediately prior to the passage of a projection |9c or 55epast cam follower 40, to a period of nearly two hours, assuming that camsegment 55 is in its reversed position as shown in .Figure 6 and thatthe thermostat satisfies the call for heat in the space to be heatedimmediately subsequent to the passage of projection |9c past camfollower 40.

Referring back to thermostat II, it has been found desirable to arrangethe contacts IIO and |22' in such manner that they will engage theiropposite contacts III) and |22 respectively at different temperatures,as for example, contact I22-I22 may make at 72 and contact IIIl-I I0' at70. This temperature may of course be adjusted to the individual heatingrequirements of the space to be heated. Assume that the temperaturefalls below 70. Both contacts |0-I Hi and |22-I22 make to close theenergizing circuit above described and energize relay |02. Upon suchenergization arm |03 will engage contact |23. The maintaining circuitabove described is'now established and stoker motor I0 continues tooperate. Now assume the temperature rises to 71. Contact II-Il is brokenbut stoker motor I continues to operate since relay ||i2 is closedthrough the maintaining circuit above described. Upon a temperature riseabove 72, however, contactsv I22-I22' break, relay |02 is deenergized,and stoker motor I9 ceases to operate. Now assume that the temperaturefalls from 72 to 71. Contact |22-I 22 makes but stoker motor Il] isnotstarted since no circuit is established. However, if the timermechanism I2 at this point energizes relay |02 through the closing ofcontacts Ilfl-IIII and contacts Hi8-m8' and actuates the stoker motor IDfor the predetermined period, it will be seen that contact II3|I3 isopen and that at the end of the time period the circuit is broken by theopening of contacts ||4-I |4 and IOS-|98 prior to the making ContactII3-I I3.

The inclusion of contact I|3| I3 in the circuit thus serves to maintainthe temperature of the space to be heated Within the normal range ofthermostat |I since, in the absence of such circuit breaking means, andassuming contact |23 to be directly connected to wire III, if relay Y|02 and motor I0 wereenergized by timer mechanism I2 withthe roomtemperature at 71 and 'therefore with contacts IIO'-| I0 and I22I22 openand closed respectively, stoker motor I0 would continue to operatethrough a holding circuit comprising transformer secondary IDIIb, WireIOI, relay coil |020., wires 91 and 99, arm ISS, Contact |23, wire II I,terminal ||2, thermo` stat II, contact I22-I22, wire |2I, switch IIS andWires ||8 and II'I, after the termination of the timed period until thetemperature reached 72 to break contact I22-I22.

The room temperature may, therefore, through the operation of contact|I3-II3 above described, be maintained constantly within the normalpredetermined differential of the thermostat as, in the illustrativeexample above given, between 70" and 72.

It will now be seen that the provision of contact H13-H3 serves topreclude actuationv of stoker motor I0 .by thermostat II while timermechanism I2 ris in control, and further that no circuit originallyenergized by timer mechanism I2 may be held through thermostat I I afterthe termination of a timed operating period in the absence of a call forheat serving to close both contacts IIO-IIII' and I22-|22.

In some instances, however, it may be desirable that the temperature bemaintained constantly above the normal diiferential of thermostat II orabove the making point of contacts lill-I I0', as in the illustrationabove, 72. In this case contact II3-||3 and its associated arm andWiring may be omitted and wire III connected directly to contact |23.Then, in the event of a temperature fall to 71 and consequent making ofcontact I22-I22, contact II-IIIJ remaining open, if the stoker isstarted and relay i122 energized by the above described action of timermechanism I2, upon the termination of the timed period of operation,stoker motor II) will continue in operation through a holding circuitcomprising transformer IElIl, wire IDI, relay |62, wires 9"! and 99, arm|03, contact |23, wire III, terminal I|2, thermostat II, Wire I2I,mercury switch II9 and wires IIB and |I'I back to transformer |00, untilthe temperature reaches 72 and contact |22-|22 breaks. It willaccordingly be seen that while contact IIS and its associated wiringforms a desirable adjunct to the system as a whole, it may be omitted ifthe operation above described is desired.

Referring now to thermostatic element |29 associated with mercury switchIIS, it lhas been found desirable in many instances to position asuitable high limit control adjacent, say, the water boiler of a heatingsystem in order to preclude an unnecessary rise in the temperature ofwater during such a transition period as, for eX- ample, from a nighttemperature of approximately to a day temperature of approximately Ithas been found that during such transition period in the absence of sucha control as indicated diagrammatically by thermo-responsive element |20and mercury switch I|9, the temperature of the water in the boiler mayrise to an unnecessarily high degree due to the prolonged action of thestoker in raising the temperature to normal day heat. Such a high limitcontrol suitably interposed in the thermostat circuit serves to cut othe stoker for sufcient periods to permit cooling of the water to normaloperating temperatures even though the position vof thermostat II stillindicates a low temperature in the space to be heated. This high limitcontrol serves, therefore, to retard continuous action of the stoker insuch a manner as to prevent unnecessary overheating of the boiler.

The inclusion of the above described control is particularlyadvantageous in mild climates where the temperature increasesveryrapidly with the y rise of vthe sun. During the night the tempera-`to furnish the requisite heat. yperature accordingly rises rapidly,whereas the ture may be relatively low and when thermostat first callsfor heat in the morning a relatively long energization of the stokermotor is required The boiler temactual temperature requirement may bepartially 'satisfied by the rise in outdoor temperature,

caused by the sun. In the absence of such a limit control as abovedescribed, the boiler temperature would rise due to the aforementioneddemand for heat, to a point suiicient toV overheat therbuildingand,under normal circumstances, a

vconsiderable time vwould elapse before the temperature could cool tothe desired level. The inclusion of the limit control therefore servesprimarilyto preclude too rapid a rise in boiler temperature in order tocompensate for a relatively rapid rise in outdoor temperature, andprevents overheating of the space to be heated due to the combinedeffects of the outdoor temperature and heating system.

A second h'igh limit control generally indicated at 132, which maycomprise a suitable stack switch, diagrammaticallyindicated by mercuryswitch I 33l and thermos-tatie element I 34, isy interposed in the linecircuit in order to provide an absolute cu-off should ther temperaturein the stack of the furnace, or, in other words, the combustiontemperature, reach a point of danger.

It may here be pointed out that in the preferred embodiment of theinvention motor I3 is connected through wires I5 and I6 to line wiresI'I and I8 between th'e high limit -control |32 and the source of powersupply, in order that the timed rotation of the cam assembly may beunaffected by the opening of mercury switch |33.

From the foregoing it will be seen that there is herein provided asystem and a specific structure which embody the features of thisinvention and achieve the objects thereof including advantages of greatpractical importance.

As many possible embodiments may be made of the above invention anad asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense. l

I claim as my invention:

1. In a control system,` in combination, a circuit, condition responsivemeans to open and close said circuit, additional means to open and closesaid circuit at predetermined time intervals, and a mechanical latchmeans movable by said condition responsive-means to latching position tomaintain' saidl additional means in open position during the period whensaid condition responsivev means closes said circuit and for anappreciable period subsequent to the opening thereof by said conditionresponsive means.

2. A circuit controlling mechanism, comprising, in combination, a relay,temperature responsive` means to openand close a circuitl through saidrelay, time controlled means to open and close a circuit through saidrelay, and means to preclude closing of said time controlled circuitduring the period when said circuit is closed by said temperatureresponsive means and immediately subsequent to reopening thereof, saidlast mentioned means comprising an arm associated with said relay andadapted upon closing of said relay to engage mechanically with said timecontrolled means. l

'3. A circuit controlling mechanism, comprising, in combination, arelay, temperature responsive means to close a circuit through saidrelay, time controlled means to close a circuit through said relay, aandmeans to preclude closing of said time controlled circuit whi-le saidtemperature controlled circuit is closed and for an appreciable periodsubsequent to opening thereof, said means comprising latch meansassociated with said relay and said time controlled means.

1. A lcircuit controlling mechanism, comprising, in combination, arelay,temperature responsive means to close acircuit through said relay,timecontrolled means to close a circuit through said relay, means topreclude closing of said time controlled circuit while said temperaturecontrolled circuit is closed and-for an appreciable period subsequent toopening thereof, said means comprising, latch means associated with saidrelay and said time controlled means, and means on said ytime controlledmeans to release said latch means after the termination of saidpredeterminedY period.

-5. A control system for stokers, including a plurality of circuits,closure of either of said circuitsV adapted to operate'said Stoker,condition responsive means including a switch to close one of saidcircuits, time controlled means including a switch to close another ofsaid circuits, means actuated by the closure of one of said switches tomaintain another of said switches open during closure of and for avariable period subsequent to reopening of said one of said switches,said means comprising mechanical latch means actuated by the closure ofone of said switches to engage the other of said switches to hold thesame in open position, and means actuated by said time controlled meansto disengage said latch means and said other switch.

6. A device of the character described, comprising, in combination, a,relay, means to energize said relay, additional means to energize saidrelay, said additional means including rotatable cam means having highand low surfaces and pivotally mounted cam follower means, thearrangement being such that engagement of said cam follower means withone of said surfaces upon rotation of said cam means energizes saidrelay, and vmeans actuated by said first mentioned means to precludepivotal movement of said cam follower means.

7. A device of the character described, comprising, in combinatiomarelay, means to energize said relay, additional means to energize saidrelay, said additional means including rotatable cam means having highland low surfaces and pivotally mounted cam follower means, thearrangementl being such that engagement of said cam follower means withone of said surfaces upon rotation of said cam means energizes saidrelay, and means actuated -by said ilrst mentioned means to precludepivotal movement of said-cam follower means, said means including alatch means associated with said cam follower means.

8. A device of the character described, comprising, in combination, arelay, means to energize said relay, additional means to energize saidrelay, said additional means including rotatable cam means having highand low surfaces and pivotally mounted rcam follower means, thearrangement being such that engagement of said cam follower means withone of said surfaces upon rotation of said cam means energizes saidrelay, means actuated by said first mentioned means to preclude pivotalmovement of said cam follower means, said means including latch means.associated with said cam follower means and means on said cam means torelease said latch means.

9.-A device of the character described, comprising, in combination, arelay, means to energize saidV relay, additional means to energize saidrelay, said additional means including rotatable cam means having khighand lov.7 surfaces and pivotally mounted cam followed means, thearrangement being such that engagement of said cam follower means withone of said surfaces upon rotation of said cam means yeriergizes saidrelay, means actuated by said rst mentioned means to preclude pivotalmovement of said cam follower means, said means including latch meansassociated with said cam follower means and means on said cam means torelease said latch means, said last mentioned means including aprojection extending a, substantial distance above said high surface.

10. A device of the character described, comprising, in combination, arelay, means to energize said relay, additional means to energize saidrelay, said additional means including rotatable cam means having highand low surfaces and pivotally mounted cam follower means, thearrangement being such that engagement of said cam follower means withone of said surfaces upon rotation of said cam means energizes saidrelay, means actuated by said first mentioned means to preclude pivotalmovement of said cam follower means, said means including latch meansassociated with said cam follower means, means on said cam means torelease said latch means and means to return said latch means tounlatching position upon release by said means on said cam means.

1l. In a control system in combination, a motor, condition responsivemeans to energize said motor through a circuit, time controlled means toenergize said motor through anothel` circuit,

means to prevent continued energization of said motor through said rstmentioned circuit after energization by said second mentioned circuitwhen said first mentioned circuit is not closed through said conditionresponsive means, said means including a switch, and means associatedwith said time controlled means to open said switch prior toenergization of said motor through said second mentioned circuit, andclose said switch subsequent to deenergization of said motortherethrough.

12. A device of the character described, comprising in combination,motor actuating means, first means to energize said actuating means,second means to energize said actuating means, said second meansincluding a revolvable cam having a high and e, low surface and a,pivoted cam follower adjacent thereto the arrangement being such thatengagement of said cam follower with one of said surfaces energizes saidactuating means, means to rotate said cam at a predetermined speedwhereby said one of said surfaces engages said cam follower atpredetermined intervals and means actuated by said first means topreclude energization of said actuating means by said additional means,said last mentioned means comprising a latch member movable by saidfirst means into latching relation with said second means.

13. In la, stoker control system, in combination, condition responsivemeans to operate said stoker, time controlled means to operate saidStoker, said time controlled means including la rotatable cam and a, camfollower, said cam follower being movable into and out of stokeroperating position according to the cam surface adjacent thereto, meansto rotate continuously said cam at a, relatively constant speed wherebysaid cam follower operates said stoker at predetermined intervals andmechanical means controlled by said condition responsive means foraffecting said cam follower to preclude operation of said stoker by saidtime controlled means during, and for an appreciable period subsequentto, operation of said stoker by said condition responsive means.

14. In a stoker control system, in combination,

14 condition responsive means to operate said stoker, time controlledmeans to operate said stoker said time controlled means including arotatable cam and a cam follower, said cam follower being movable intoand out of stoker operating position according to the cam surfaceadjacent thereto, means to rotate said cam at a relatively constantspeed whereby said cam follower operates said stoker at predeterminedintervals and mechanica1 means controlled by said condition responsivemeans to preclude operation of said stoker by said time controlled meansduring, and for an appreciable period subsequent to, operation of saidstoker by said condition responsive means, said last mentioned meanscomprising a latch movable upon operation of said stoker by saidcondition responsive means to engage said time controlled means.

15. In a stoker control system, in combination, condition responsivemeans to operate said Stoker, time controlled means to operate saidstoker, said time controlled means including a rotatable cam and a camfollower, said cam follower being movable into and out of stokeroperating position according to the cam surface adjacent thereto, meansto rotate said cam at a relatively constant speed whereby said camfollower operates said stoker at predetermined intervals, and mechanicalmeans controlled by said condition responsive means to precludeoperation of said stoker by said time controlled means during and for anappreciable period subsequent to operation of said stoker by saidcondition responsive means, said last mentioned means comprising a latchmovable upon operation of said stoker by said condition responsive meansto engage said time controlled means, and tripvmeans associated withsaid cam to release said latch means after a desired interval.

16. In a control system, a motor, a relay adapted to operate said motor,a thermostat adapted to energize said relay, time controlled mechanismalso adapted to energize said relay, said mechanism comprisingrevolvable cam means, means to revolve said cam means at a relativelyconstant speed, cam follower means operated by said cam means and meansoperated by said cam follower means to Operate said relay upon operationof said cam follower means by said cam means, and means operated by saidrelay to prevent operation of said cam follower means to a relayenergizing position by said cam means during energization of said relayby said thermostat.

17; In a stoker control system,'in combination, condition responsivemeans to operate said stoker, time controlled means to operate saidstoker'said time controlled means including a rotatable cam and a camfollower, said cam follower being movable into and out of Stokeroperating position according to the cam surface adjacent thereto, meansto rotate said cam at a relatively constant speed whereby said camfollower operates said stoker at predetermined intervals and mechanicalmeans controlled by said condition responsive'l means to precludeoperation of saidl stoker by said time controlled means during, and foran appreciable period subsequent to, operation of said stoker by saidcondition responsive means, said last mentioned means comprising a latchmovable upon operation of said Stoker by said condition responsive meansto engage the cam follower of said time controlled means, said lastmentioned means comprising an arm and a lever adjacent said cam means,the arrangement being such that `essere l15 said arm upon movement ofsaid relay engages "`aid ylever and through said lever holdssaid cam followermeans. l18A circuit controlling mechanism, comprising, incombination, a relay, a temperature re- 'sponsiv'e means to open andclose a circuit through "said relay, time `controlled means to open andclose a circuit through said relay, said time 'controlled'meanscomprising, in combination, cam means, cam follower means operated bysaid cam means, means to rotate continuously said "cam'means at apredetermined speed whereby 'said cam follower means'is operatedatpredetermined time intervals and circuit controlling means operated bysaid cam follower means to close said iir'fciiity at predetermined timeintervals, and means associated with said temperature responsive meansto prevent operation of said cam follower means to a relay energizingposition by said cam means when said circuit is closed'by saidtemperature responsive 'means and for an appreciable `Aperiodvafteropening of said circuit by said. tem- ''peiatu're responsive means.

19. In a control system, a motor, a relay adapted to'operate said motor,a. thermostat adapted to energize said relay, time controlled mechanismalso adapted to energize said relay, said mecha- Arii'srn comprisingrevolvable cam means, means "to'revolve said cam`means at a relativelycon- 'stant speed, cam follower means operated by said cam means andmeans operated by said cam follower means to operate said relay uponoperation of said cam follower means by said cam means, and meansoperated by said relay to prevent oper- Yation to a relay energizingposition of said cam follower means by said cam means duringenergizatio'n of saidI relay by said thermostat, and to vmaintainsaidcam follower means inoperative for an appreciable period subsequenttof opening of said circuit by said temperature responsive means. 20. Ina control system, the combination of, a motor,` means including a firstcircuit in control of said motor, control means for closing the rstcircuit to cause operation o-f said motor, a second circuit in 'controlof said motor, periodically operated contro-l means for periodicallyclosing the Vsecond circuit to cause periodic operationof said motorincluding continuously operated cam means and means controlled'by themeans including the first circuit and directly and positively operatedupon every closure of the first circuit' to preclude closing of thesecond circuit for an'appreciable period subsequent to opening of saidirst circuit.

21. In a control system, the combination of, a motor, means including arst circuit in control of said motor, control means for closing thefirst circuit to cause operation of said motor, a second circuit incontrol of said motor, periodically operated control means forperiodically closing the second circuit to cause periodic operation ofsaid motor including continuously operated cam means, means foradjusting the cam means to v ary the duration of the period of operationof the motor, and means controlled by the means lincluding the rstcircuit and positively operated upon every closure of the first circuitto preclude closing of the second circuit for an appreciable periodsubsequent to opening of the first circuit. 22. A stoker control systemcomprising, in combination, a plurality of circuits, condition`responsive means to operate said stoker through one of said circuits,time controlled means to operate said stoker through another of saidcircuits, and means to prevent continued operation of said stokerthrough said circuit of said condition responsive means after originalenergiza- 'tion of said stoker through said circuit of said timecontrolled means in the absence ofcondition change sufficient to causeenergization of the stoker by said condition responsive means, s aidmeans including a make and break contact in the circuit controlled bysaid condition responsive means, the arrangement being such that saidcontact is opened by said time controlled means prior to closing of saidtime controlled circuit and reclosed by said time controlled meanssubsequent to reopening of said time controlled circuit.

23. In a heating system for a space having heating means for the spaceand a stoker for firing the heatingmeans, the combination of, a relayhaving a control winding, a maintaining switch and a load switch for thestoker, the maintaining switch and the load switch beingl closed whenthe control winding is energized, a space thermostat having a pair ofswitches that are sequentially closed upon a decrease in spacetemperature, means for completing a starting circuit through the controlwinding of the relay and the last to close switch ofthe thermostat toclose ythe Amaintaining switch and the load switch for startingoperation of the stoker, means for completing a maintaining circuitthrough the control winding of the relay, the rst to close switch of thethermostat and the maintaining switch to completing a circuit throughthe control winding of the relay and the periodically operated iirstswitch to close periodically the maintaining switch and the load switchto operate vperiodically the stoker independently of the thermostat,said second timer operated switch being included in the maintainingcircuit to prevent continued operation of the stoker following a timedoperation when only the first to make switch of the thermostat isclosed.

24. In apparatus of the character described, rin combination, switchmeans, timing means for normally periodically causing closing andopening operation of the switch means, additional means for causingclosing and opening operation of the switch means at indeterminatetimes, and mechanism comprising latch means controlled by both theadditional means and timing means whereby normally after a closing andopening operation of the switch means caused by the additional means thetiming means is rendered temporarily ineffective to cause closing andopening operation of the switch means and is then rendered eiectiveagain so that a longer than normal period elapses before another closingand opening operation of the switch means is caused by the timing means.

25. A device of the class described, comprising, in combination, aswitch, means to open and close said switch and including cam meansrotatable at a substantially constant speed and associated cam followermeans to open and close said switch in accordance with a predeterminedschedule, Ysaid means to open and close said switch also including anadditional means for opening and closing said switch, and meansassociated with said cam means and said cam follower means and connectedto said additional means lfor actuation 17 thereby each time saidadditional means actuates said switch to prevent operation of saidswitch by said cam means and cam follower means at one of its scheduledtimes upon operation of said switch by said additional means during apredetermined different portion of said schedule.

26. Ina timing mechanism of the class described, in combination, adevice to be operated, timing means to move said device to a rstposition and then back to its original position according to apredetermined schedule and including rotatable cam means and associatedcam follower means, additional means by which said device may be movedto its first position and then back to its original position at timesdiffering from said predetermined schedule, and means associated withsaid timing means and connected to said additional ymeans for directactuation thereby by which operation of said device by said additionalmeans during a predetermined part of said schedule when said devicewould not be operated by said timing means prevents operation of saiddevice to said first position by said timing means at a different andlater portion of said schedule.

27. In a timing mechanism of the class described, in combination, adevice which it is desired to move from a first position to a secondposition and then back to its rst position, constantly rotatable cammeans and associated cam follower means for moving said device to saidsecond position, maintaining it therein for a predetermined time andthen returning it to said first position upon constant rotation of saidcam means, adjusting means associated with said cam means and camfollower means for varying the length of time said device will bemaintained in its second position without affecting the periodicity atwhich said device will be moved to said second position during constantrotation of said cam means and for independently varying the number oftimes said device will be moved to its second position during a givenperiod of time without aiecting the length of time said device will bemaintained in said second position, additional means independent of saidcam means by which said device can be moved to its second position whilesaid cam means is being rotated, and means cooperating with said devicenormally to prevent its being moved to said second position by said cammeans and cam follower means if said device has been moved to its secondposition and back to its first position at a predetermined time otherthan that caused by said cam means and cam follower means.

28. In a control system, the combination of, a motor, means including afirst circuit in control of said motor, control means for closing thefirst circuit to cause operation of said motor, a second circuit incontrol of said motor, periodically operated control means including cammeans moved at a constant speed for periodically closing the secondcircuit to cause a predetermined number of periodic operations of saidmotor upon a given movement of the cam means, means for adjusting thecam means to increase or decrease the number of periods of operation ofthe motor for a given movement of the cam means, a single means foradjusting the cam means to simultaneously vary the duration of all theperiods of motor operation, and means controlled by the means includingthe first circuit and positively operated upon every closure of theiirst circuit to preclude closing of the second circuit for anappreciable period subsequent to opening of the first circuit.

29. In a control system, the combination of, a motor, means including afirst circuit in control of said motor, control means for closing thelrst circuit to cause operation of said motor, a second circuit incontrol of said motor, periodically operated control means including cammeans moved at a constant speed for periodically closing the secondcircuit to cause a predetermined number of periodic operations of saidmotor fora given movement of said cam means, means for adjusting saidcam means to vary the number of periods of operation of said motor for apredetermined movement oisaid cam means while automatically maintainingthe duration of all of said periods equal to each other, and meanscontrolled by said means including the rst circuit and positivelyoperated upon every closure of said first circuit to preclude closing ofthe second circuit for an appreciable period subsequent to open.. ing ofsaid irst circuit by said rst mentioned control means.

30. A device of the character described, comprising, in combination, acircuit, means to close said circuit, additional means to close saidcircuit, said additional means includingrotatable cam means havingactive and inactive surfaces and cam follower means adjacent thereto,the arrangement being such that engagement of said cam follower withsaid active surfaces closes said circuit, means to rotate said cam at apredetermined speed whereby said active surfaces engage said camfollower means at predetermined intervals, and means positively anddirectly actuated by said iirst mentioned means upon every operationthereof normally to preclude the next subsequent closing of said circuitby said additional means.

31. In a control system in combination, a motor, condition responsivemeans to energize said motor through a circuit, a maintaining circuitfor said motor controlled by said condition responsive means, timecontrolled means to energize said motor through another circuit, andmeans to prevent continued energization of said motor throughr saidmaintaining circuit after original energization through the other ofsaid circuits in the absence of condition change sufficient to causesaid condition responsive means to initially energize said motor.

32. In a control system in combination, a motor, condition responsivemeans to energize said motor through a circuit, a maintaining circuitfor said motor controlled by said condition responsive means, timecontrolled means to energize said motor through another circuit andmeans to prevent continued energization of said motor through saidmaintaining circuit after original energization by said last-mentionedcircuit in the absence of condition change suicient to cause saidcondition responsive means to assume motor energizing position.

33. A device of the character described, comprising in combination,motor actuating means, rst means to energize said actuating means,second means to energize said actuating means, said second meansincluding a revolvable cam having a high and a low surface and a pivotedcam follower adjacent thereto the arrangement being such that engagementof said cam follower with one of said surfaces energizes said actuatingmeans, means to rotate continuously said cam at a predetermined speedwhereby said one of said surfaces engages said cam follower atpredetermined intervals to energize said actuating means atpredetermined intervals and means positively and directly actuated bysaid first; means upon Number every operation rthereof to precludeenergization 2,107,472 of said actuating means by said second means2,141,024 for an appreciable period subsequent to termi- 1,386,698

-nation of Venergization of said actuating means 5 Re. 19,164

by said first means. 2,055,641

ELMER K. SCOGGIN. Re. 21,350

REFERENCES CITED 1,960,718

The' following references are of record in the lo 111e of this at nt: 1

UNITED STATES PATENTS Re 20 240 Name Date Halvorson May 3, 1932 15Number 20 Name Date Denison Feb. 8, 1938 Staley Dec. 20, 1938 GarrisonAug. 9, 1921 Teeple May 15, 1934 Young Sept. 29, 1936 Miller Feb. 13,1940 Taylor Sept. 5, 1933 Standifer et a1 May 29, 1934 Bardes July 10,1934 Teeple Sept. 11, 1934 McCabe Apr, 4, 1939 Owens Jan. 12, 1937

